top of page


By Steve Haag, RPT 


1. Pianos are built and designed to remain at 42% humidity (that's 8% moisture content in the wood).


2. It is not desirable to keep your whole house or building at 42% humidity in the winter because of the high vapor pressure that results (see below for more information about this).


3. Unless a piano is humidity controlled, it is impossible to keep it tuned to A-440.


4. A humidity change of only 10% can make the piano noticeably out of tune, even if it was tuned only two days before. A tuner cannot account for changes in humidity!


5. You cannot depend on cheap dial humidity gauges. They are grossly inaccurate at the lower and upper ends of the scale where the information is most important. Choose a digital hygrometer instead.


6. A piano tuned to A-440, at 42% humidity, has 18 to 20 tons of tension on it. When the humidity goes high the tension will increase, causing the pitch to go sharp. When the humidity goes low the tension will decrease, causing the pitch to go flat. When either of these happen, the piano must undergo a pitch correction to get the piano back to A-440. This pitch correction is a rough tuning which involves a massive tightening (if flat) or loosening (if sharp) of the strings to get the "stretch" out and to make the subsequent fine tuning more stable.



Cracking of sound board

"Singing" dampers

Cracking of bridges

Rusty strings

Cracking of pin block (loose tuning pins)

Sticky keys

Loose action screws

Felt coming unglued

Bottom of piano coming loose

Piano going out of tune


8. You can counteract all of the problems mentioned above by installing a humidity control system right inside your piano. This system has a five-year warranty, is noiseless, runs by electricity and costs less than three dollars per month to run. The five-part system consists of the following:

DAMPP-CHASER Dehumidifier --  A long heating element that raises the temperature and thus lowers the relative humidity.


Dual Automatic Humidistat -- Senses the humidity level and turns on and off the humidifier and dehumidifier as needed.


Humidifier -- A bucket of water with a heating element and cloth wicks (pads).


Low Water Warning Light -- Mounted under the keyboard.


Watering Kit -- Easy-Fill Tube and Two Quart Can so you can refill the humidifier without having to open up the piano.


9. This Five Part Dampp-Chaser Piano Life Saver System can be installed in grands and uprights. Also available is the Dehumidifier and Humidistat alone for grands and for uprights.


Prices subject to change. Please call or email me for current prices. I have only the Dehumidifier and Humidistat in my piano at home and highly recommend these two items for every piano. These systems can be purchased from: Steve Haag, RPT Third Generation Piano Tuner-Technician 515-278-4840 




IN THE WINTER, because of the heating system, the humidity level will go down. The more often the heat comes on, the drier it gets. However, any attempt to attain 42% humidity when outside temperatures are below 30° F., will result in damage to your home! This is because the high humidity and temperature inside create a higher vapor pressure than outside. This pressure tries to equalize by traveling through the walls and/or ceiling to the outside. The air and moisture then meet freezing conditions at some point within the wall or ceiling. The moisture condenses, freezes and expands, creating openings that grow larger with each cycle. The safe indoor relative humidity percentage is not a fixed number but will fluctuate with the outdoor temperature. All central humidity control systems have recommended humidity settings based on outside temperature as follows:



+30° F               35%

+20° F               35%

+10° F               30%

   0° F                25%

-10° F                20%

-20° F                15%

(These settings are recommended by both the American Society of Heating, Refrigeration and Air Conditioning Engineers and the National Environmental Systems Contractors Association.)


The result of following this advice, however, is that room humidity levels will be lower than those desired to maintain piano stability. The obvious solution to this problem is to humidify only the article that requires the higher level. This is exactly what the Dampp-Chaser Piano Life Saver System is designed to do. 

IN THE SUMMER, early morning humidity levels can run 90% and above. Daytime levels fall as the temperature rises, but still the average for the 24-hour period can be 70-80%. In some buildings air conditioners can lower inside humidity to around 60% depending on the outside temperature, but are not able to affect humidity at all when the compressor is not running or (of course) when they are turned off. The net result is a humidity level that will generally average significantly above 60%. The moisture content of the wood in your piano will generally continue to increase through the fall until the heating system is turned on. 


SUMMARY: Despite the benefits provided by room humidification in the winter and air conditioning in the summer, there is a strong probability that the room humidity levels will still fluctuate by 30-50% between summer and winter. The Dampp-Chaser Piano Life Saver Humidity Stabilization System will allow a fluctuation of only 8% maximum from summer to winter. It provides humidity control within the piano rather than trying to perform the impossible task of controlling the entire surrounding area to the level necessary for proper stabilization and preservation of your piano. Visit for more information.

Fact #2
bottom of page